The investigator has been studying the mechanisms that control retinal development, and now proposes to study the cell cycle regulatory proteins to define their role in this process. The two basic aims of the research program are to determine: (1) whether the differences in proliferation behavior of progenitor cells at different times in retinal development are due to intrinsic or extrinsic differences; and (2) whether any of the known cell cycle genes contribute to the cycling behavior of retinal progenitor cells and the types of progeny they produce. The investigator proposes to use a combination of in vitro and in vivo approaches to address these questions.